The invention relates generally to the field of transformers and more particularly to transformer applications requiring multiple transformer functions.
Transformers are used extensively for various different purposes. A well-known transformer use is to change voltage levels between a voltage supplied and a voltage to be used by an electronic device. Such a transformer is typically a core with a winding. Transformers for power applications of course vary and include transformers for high voltage applications and transformers for relatively low voltage applications.
Transformers are also used extensively for signal applications. Communications applications often use signal transformers. Such a signal transformer is used at low voltage levels for isolating a transceiver from the communications medium. This will be for example an Ethernet isolation transformer used to separate the transmitter and receiver of an Ethernet card or similar device (e.g., network interface card for NIC).
Ethernet isolation transformers are typically provided as a small package mounted on the Ethernet printed circuit board. The transformer has its connections appropriately connected to contacts on the board. The Ethernet isolation transformers (e.g., for IEEE 802.3 applications) are typically provided with very small windings and a very small ferrite core. The structure is provided with a plastic package and digital interface pins (e.g., 16 pins). The entire structure may be, for example, xc2xc in. to xc2xd inch.
The IEEE 802.3 standard (ETHERNET) has no current provisions for supplying power to Ethernet devices. One proposal for supplying power is to provide the power on the Ethernet connection, namely the transmission medium. The issues as to supplying power involve issues as to the environment of the system as well as in the overall costs.
Providing power locally presents problems for Ethernet applications. One example of a problem encountered is the security camera problem wherein the local supply of power can be problematic as to the secure status of such a security camera. A possible solution is to provide the transmission medium as a medium for supplying power (the Ethernet wire is used for supplying power). However, this involves some problems as well.
Another network device which has been increasingly used in network environments is a network phone. Such a phone device converts audio analog signals into digital signals and sends the digital signals out in the form of packets over a network such as a local area network ( LAN). The phone devices can be provided with a power circuit which is integrated into the phone. The AC power is applied to the phone and the power is conditioned (e.g., rectified) and possibly also converted by a transformer.
A changeover from the approach of supplying power locally to a system involving supplying power via the network wires involves various problems including the need to condition the power supplied over the wire. One significant problem is the need to supply the power over the network wires at a relatively high voltage level. For example, the use of 45 volts AC or greater voltage over the wire is considered to be advantageous. However, the use of high voltage levels results in higher cost with regard to semiconductor devices used in the network device. Typically, voltage levels below 30 volts are desirable with regard to maintaining semiconductor unit costs at a low level. Semiconductor devices which use higher voltage levels typically result in higher costs.
It is an object of the invention to provide a transformer unit with a single package having an integrated signal transformer and power transformer.
It is another object of the invention to provide a transformer unit with a single package which can be mounted on a circuit board of a network device and which can connect to network wires which wires carry a signal with a power component and a communications signal component and which transformer unit transforms the signal to provide a power signal at a lower voltage value and which transformer unit isolates the network transceiver of the circuit board from the signal carried by the wires.
It is a further object of the invention to provide a unit with input connections which are connected to a transmission media and output connections which are to be connected to a communications printed circuit board (PCB) and which cooperates with the PCB to form a network device and which unit includes a signal transformer and a power transformer and the transmission media carries both a power signal to power the network device and carries communications signals to and from the network device.
According to invention, a transformer unit is provided including and isolation transformer and a power transformer. The isolation transformer and the power transformer are provided as part of a single package or within a single housing having a plurality of connection pins. The connection pins include Ethernet wire connection pins connecting to e.g. 45 volts AC wires. The wires may be the typical Ethernet Tx+, Txxe2x88x92, Rx+, Rxxe2x88x92 lines. However, the transformer unit is preferably used wherein the wires carry a 60 Hz 48 V AC signal (60 Hz ISO 48 V poential) between the Tx+ and Txxe2x88x92 and the Rx+ and Rxxe2x88x92. In addition, the Tx+ and Txxe2x88x92have a series superimposed plus 2V pulse. The Rx+ and Rxxe2x88x92 have a series superimposed plus 2V pulse. Additionally, the connection pins of the transformer unit include transformer output pins providing 12 volts AC to the circuit board of the network device. Additional output pins are provided including Tx+, Txxe2x88x92, Rx+ and Rxxe2x88x92, which signals are isolated by the isolation transformer portion of the transformer unit.
The unit preferably includes a power transformer portion including a core and a winding with two isolation transformers each including a core and windings. The isolation transformers each include a center tap, which may be used to eliminate noise (electromagnetic interference).
It is still another object of the invention to provide a process for connecting transmission lines carrying a power signal component and a transmission signal component to a network device which uses the power supplied by the network transmission lines.
According to a further aspect of the invention, a process is provided for connecting a network device, including providing a single unit with integrated isolation transformers and power transformer. The unit is connected to 4 transmission lines carrying a network signal and power signal (a signal with a power component and with a network communications signal component). A first isolation transformer in the unit isolates transmission signals on the sending transmission lines from a transmitter of the device. A second isolation transformer in the unit isolates transmission signals on the receiving transmission lines from a receiver of the device. Each of the first isolation transformer and second isolation transformer are connected to the power transformer, which supplies power to the circuit board of the device.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.